1. Field of the Invention
The present invention relates to a wafer processing apparatus, a wafer processing method, and a semiconductor substrate fabrication method and, more particularly, to a wafer processing apparatus for processing a wafer by dipping it into a processing solution, a wafer processing method, and a semiconductor substrate fabrication method.
2. Description of the Related Art
Cleaning processing is a typical example of wafer processing. One subject of wafer cleaning is to increase the speed. Japanese Patent Laid-Open No. 8-293478 has disclosed a wafer cleaning method capable of increasing the cleaning efficiency by supplying ultrasonic waves while rotating a wafer, and an apparatus for practicing this method.
The wafer cleaning method disclosed in Japanese Patent Laid-Open No. 8-293478 is based on the recognition that a wafer is most efficiently cleaned at the interface between a cleaning solution and ambient atmosphere. In the wafer cleaning method, therefore, particles inevitably attach to a wafer at the interface between the cleaning solution and ambient atmosphere.
In the wafer cleaning apparatus disclosed in Japanese Patent Laid-Open No. 8-293478, a cam mechanism for rotating a wafer is arranged immediately below the wafer, so a rotating force is not efficiently transmitted to the wafer. In the wafer cleaning apparatus, the transmission of ultrasonic waves is interrupted because the cam mechanism is laid out to completely shield the wafer from below. As a result, the strength of ultrasonic waves differs between the center and peripheral portion of the wafer, and the wafer cannot be uniformly processed. This nonuniformity cannot be improved by rotation of the wafer.